Abstract

The elaborate networks and the crosstalk of established signaling molecules like salicylic acid (SA), jasmonic acid (JA), ethylene (ET), abscisic acid (ABA), reactive oxygen species (ROS) and glutathione (GSH) play key role in plant defense response. To obtain further insight into the mechanism through which GSH is involved in this crosstalk to mitigate biotic stress, transgenic Nicotiana tabacum overexpressing Lycopersicon esculentum gamma-glutamylcysteine synthetase (LeECS) gene (NtGB lines) were generated with enhanced level of GSH in comparison with wild-type plants exhibiting resistance to pathogenesis as well. The expression levels of non-expressor of pathogenesis-related genes 1 (NPR1)-dependent genes like pathogenesis-related gene 1 (NtPR1), mitogen-activated protein kinase kinase (NtMAPKK), glutamine synthetase (NtGLS) were significantly enhanced alongwith NtNPR1. However, the expression levels of NPR1-independent genes like NtPR2, NtPR5 and short-chain dehydrogenase/reductase family protein (NtSDRLP) were either insignificant or were downregulated. Additionally, increase in expression of thioredoxin (NtTRXh), S-nitrosoglutathione reductase 1 (NtGSNOR1) and suppression of isochorismate synthase 1 (NtICS1) was noted. Comprehensive analysis of GSH-fed tobacco BY2 cell line in a time-dependent manner reciprocated the in planta results. Better tolerance of NtGB lines against biotrophic Pseudomonas syringae pv. tabaci was noted as compared to necrotrophic Alternaria alternata. Through two-dimensional gel electrophoresis (2-DE) and image analysis, 48 differentially expressed spots were identified and through identification as well as functional categorization, ten proteins were found to be SA-related. Collectively, our results suggest GSH to be a member in cross-communication with other signaling molecules in mitigating biotic stress likely through NPR1-dependent SA-mediated pathway.

Notes

Acknowledgments

We gratefully acknowledge Prof. Jack M. Widholm, Department of Crop Science, University of Illinois, USA for providing us seeds of Nicotiana tabacum cv. Xanthi, Dr. Geoffrey Duby, Université Catholique de Louvain, Belgium for providing tobacco BY2 cells and Prof. Siddhartha Roy for sharing his expertise regarding the application of 2-DE and its analysis. We acknowledge the help and support provided by Dr. Maitreyee Banerjee and the staffs of Greenhouse, West Bengal State Council of Science and Technology, Salt Lake, Kolkata, India, throughout the study period. This work was supported by the Department of Science and Technology (DST), New Delhi, India, and partly by the Council of Scientific and Industrial Research (CSIR), New Delhi, India. Research activities by Srijani Ghanta, Dipto Bhattacharyya, Ragini Sinha and Anindita Banerjee have been supported by fellowships from CSIR, New Delhi, India.